Modern industrial processes often require exact placement of die-cut, slit, formed or molded patterns which are intricately-shaped, or have thin or narrow segments. Such patterns are often made of metals, foils, cured epoxies, or gasket materials. For example, in the manufacture of personal communication devices (e.g., cellular phones or pagers) extremely intricately shaped electromagnetic interference (EMI) gasket materials must be produced, manipulated, and installed into such devices to exacting tolerances. Heretofore, such process steps have been tedious, costly, and laborious.
Previously, in the field of EMI shielding gaskets, V-shaped strips of silicone-filled elastomers have been hand placed onto a molded or machined rib, or into a predetermined groove on a circuit board cover. Also, die-cut metalized fabrics wrapped over foam strips with an integral adhesive, and die-cut patterns of oriented metal wire embedded in a support substrate have been used. Typically, these patterns are hand-cut, separately packaged and stored. Thereafter, these patterns are hand-applied and oriented visually onto a substrate by an end user. Because of the difficulty in manipulating these delicate, small and intricate patterns by hand, widths of the gasket are often forced to be greater than desired. This is undesirable considering the high value of space on today's tightly-packed printed circuit boards. Also, the manipulation of these gaskets is tedious, ergonomically hazardous, and therefore, quite costly, since it almost always is extremely time-consuming. In some cases, installation times can exceed several minutes per part, depending upon the complexity of the part.
One suggested attempt generally known in the art is directed at increasing the efficiency of these manufacturing processes and teaches semi-automatically dispensing liquid-gasket compounds onto a desired substrate. However, because such liquid-gasket compounds require a curing period, have limitations in terms of width-to-height ratios, and require expensive installation equipment, this method is not optimal.
Another method of positioning, applying and manipulating adhesive-backed gaskets, (or non-adhesive backed gaskets) or other similar materials, is disclosed in U.S. Ser. No. 08/215,124. As disclosed therein, a method and apparatus is presented for applying flexible gasket strips to a surface. More particularly, the invention of U.S. Pat. No. 5,536,342 relates to an automated system using a robot guided head to manufacture gasket patterns, and is particularly suitable for applying gasket strips to electronic circuit boards with a placement accuracy of about .+-.0.005". Typically, the gasket strips applied by the disclosed apparatus have a thickness dimension of from about 0.01" to about 0.125" and a width dimension of from about 0.04" to about 1". The gasket strips are applied in a manner which does not stretch or elongate the gasket strip material. Broadly, the apparatus directs a robot with a controller to apply the gasket strip to the substrate. The robot is then moved to advance a length of strip onto the substrate, the advancing strip being guided onto the substrate in the desired position. The controller actuates the cutting of the strip to the desired length. These steps can be repeated to apply additional strips as necessary to form the desired gasket pattern. Such a method and apparatus is extremely useful when material cost is at a premium, and where the material width is consistent throughout the application. However, since the method of die-cutting or molding offers distinct advantages when the desired patterns become very complex, or where material widths vary, a method to accurately and quickly apply these die-cut patterns is also quite valuable.
In addition to the foregoing, another shortcoming of the current methods for producing intricate patterns in various materials exists in the fabrication of such patterns with conventional dies. This shortcoming is consistent with many dimensioning procedures, such as but not limited to, die-cutting, forming, molding or slitting materials, for example, and manifests itself in the difficulty of removing the desired material from the die quickly, efficiently, and without damage to the dimensioned material. In many instances as well, the material to be cut, manipulated, and installed has a high-aspect ratio--meaning that the width of the material is substantially less than the height of the material in certain areas of the pattern. More particularly, EMI gaskets having a height of 0.100 inches (or more) and a width of 0.050 inches (or less) are often desired in many applications, such as but not limited to personal communication devices or PCMCIA applications. Such an aspect ratio of 2:1 is considered to be a high-aspect ratio. Presently, there are no known cost-effective procedures to produce, manipulate, position and effectively install such unstable-shaped articles, since these patterns do not readily release from their die, and are very difficult to handle without damaging. The foregoing difficulties are compounded when such articles are intricate, and comprised of a material that is soft, compliant, and susceptible to compression-set when over-compressed.
Over-compression is especially prevalent in the die-cutting industry, and is primarily a result of the large surface area of the inside cutting-edge walls of the die. In the case of forming high-aspect ratio shaped articles, conventional ejection material is located inside the die, and/or the die is necessarily deeper because of this high-aspect ratio. As is well known, for extremely resilient materials, such as foams, for example, high-aspect ratio die-cutting is not difficult, since these materials easily recover from over-compression, and the die doesn't have to be as deep, which reduces the inside die-wall surface area and makes part ejection easier. In addition to forming high-aspect ratio articles, even very low-aspect ratio articles (e.g., articles having an aspect ratio of about 1:8, and having dimensions of 0.010 inches high.times.0.080 inches wide) currently have no cost-effective method for their manipulation and/or installation once fabricated, even though their ejection is less difficult during manufacture.
It should be understood, that similar shortcomings exist anywhere patterned materials are fabricated, dimensioned, positioned, manipulated and/or installed, such as but not limited to the field of molded environmental gaskets or formed metal foil covers.
The foregoing illustrates limitations known to exist in present processes for accurately dimensioning and manipulating materials. Thus, it is apparent that it would be advantageous to provide an improved process directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.